QFile: fix undefined behavior when closing a buffered file

C11 §7.21.3.4 [Files] says that

    The value of a pointer to a FILE object is indeterminate
    after the associated file is closed

POSIX.1-2013 reinforces by saying that

    After the call to fclose(), any use of stream results
    in undefined behavior.

This means we can't call fclose() again on a FILE *,
even if fclose() returned EOF and set errno to EINTR.

Change-Id: I282f4ff926e3c134729defa290c80d42431e97ce
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>

1 files changed, 9 insertions, 13 deletions

diff --git a/src/corelib/io/qfsfileengine.cpp b/src/corelib/io/qfsfileengine.cpp
index 1ae182a4c1..e198cd6d75 100644
--- a/src/corelib/io/qfsfileengine.cpp
+++ b/src/corelib/io/qfsfileengine.cpp
@@ -168,10 +168,7 @@ QFSFileEngine::~QFSFileEngine()
     Q_D(QFSFileEngine);
     if (d->closeFileHandle) {
         if (d->fh) {
-            int ret;
-            do {
-                ret = fclose(d->fh);
-            } while (ret == EOF && errno == EINTR);
+            fclose(d->fh);
         } else if (d->fd != -1) {
             int ret;
             do {
@@ -375,15 +372,14 @@ bool QFSFileEnginePrivate::closeFdFh()
     // Close the file if we created the handle.
     if (closeFileHandle) {
         int ret;
-        do {
-            if (fh) {
-                // Close buffered file.
-                ret = fclose(fh) != 0 ? -1 : 0;
-            } else {
-                // Close unbuffered file.
-                ret = QT_CLOSE(fd);
-            }
-        } while (ret == -1 && errno == EINTR);
+
+        if (fh) {
+            // Close buffered file.
+            ret = fclose(fh);
+        } else {
+            // Close unbuffered file.
+            EINTR_LOOP(ret, QT_CLOSE(fd));
+        }
 
         // We must reset these guys regardless; calling close again after a
         // failed close causes crashes on some systems.